Model aeroplane



Nov. 14, 1933. c. M. WILMOT ET AL MODEL AEROPLANE Filed March 24, 1931 2 Sheets-Sheet 1 Nov; 14, 1933. c. M. WILMOT ET AL MODEL AEROPLANE 1931 2 Sheets-Sheet 2 Filed MaICh 24 Patented Nov. 14, 1933 MODEL AEROPLANEC- Charles Mandeville Wilmot and John Mandeville Wilmot, London, England Application March 24, 1931, Serial No. 525,004,-

r and in Great Britain March 31, 1930 18 Claims. (or. 46-50) I mum power when it is fully wound up and decreasing power as it unwinds. In'fact, owing to the high initial pull practically every existing model aeroplane employing an elastic motor rapidly loses stability after leaving the ground. It is one object of thepresent invention to produce greater uniformity of pull during the flight of a model aeroplane than'has been possible hitherto. A further object of the present invention is to reduce the wingspan of a model aeroplane to twelve inches or less and yetto produce an efficient model actually capable of flight.

' One feature of our model aeroplane consists of the use, as the source of power, of one or more elastic motors connected by step-up gearing to an airscrew in such a way that the torque exerted by the motor or motors upon the aeroplane is in the opposite sense to the torque exerted by the air screw upon the aeroplane. We have found that by thus opposingthe two torques and simultaneously causing the air screw to rotate faster than the elastic motor or motors, a model aeroplane ofsmall 'sizeoan be produce which is more stable and has'a'longer flight than any existing model aeroplane of relatively smallsize and power.

We find it'preferable to employ a single'multiple strand motor and to fix one end of it directly to a gear wheel mounted ina small metal ca'sing at the front end of the fuselage to gear with a smaller wheel connectedto the air screw. .Then when the elastic motor is fully wound up there is a very considerable pull upon the first gear wheel, with the result that thereis considerable frictional resistance to its rotation but no corresponding frictional resistance to the rotationof the air screw. As the motor gradually unwinds and so exerts less pull, the frictional resistance decreases thuscompensating to some extent for the loss of power. This allows a more uniform pull to be exerted by the air screw than is the case when the airscrew and elastic motor both are directly connected to a single bearing, which then acts as a floating bearing. Furthermore, in our construction, owing to the relatively high speed of the air screw dueto the intervention of the gearing, there is an increased drag upon the 55 blades which tendsto hold the motor back initially.

It is a further great advantage that owing to the high rate of revolution of the air screw, the be reduced to its correct relative latter may I size and shape. This is impossible in model aero planeshaving directly driven air screws, and ow- 0 I ing to the large diameters of the air screws in such aeroplanes it is necessary to provide a dispropor-. tionately long undercarriage to give adequate ground 'clearanceand a large tail to counteract the torque. By means, however, of the present invention the parts are all arranged in their proper proportion. I

A further object-of the present invention is to make the wings hollow and yet strong enough for the aeroplane to fly. We have found that go this can be efiected if we make the fuselage of, a single tube containing the motor or motors but without any internal longitudinal framework; Preferably this tube is made of a material such as very thinsheet aluminium, in which case it will not require any internal frameworkwhatever, but in some cases it may be made of a material such aspaper and be provided with one or two internal'reinforcing rings to resist lateral pressure. Then the wings maybe made hollow without any internal framework at all. Preferably they are mounted upon 'the fuselage by means of cross spars passing completely through the fuselage and entering ribs at the inner ends of the wings. The wings may be 5 made of paper or like material and their shape may be imparted to them by the ribs. The method 'of determining the mostsuitable shape of wing and of "obtaining this by making the'rib of a certain shape constitutes an important feature of the invention, and will be described in greater detail below. A hollow construction of the wings without anyinternal framework is rendered possible by the fact that the tubular fuselage and other parts are very light and that conse-i quently it isnot necessary to provide an internal framework to the wings to take the stresses involved. Equally the jabolition of the internalframework introduces a'reduction in weight of the whole model aeroplane landthus allows the whole to be made smaller than has hitherto been regarded as possible. e

In order that the invention may be clearly understood and readily carried into effect, onemodel aeroplane constructed in accordance therewith will now be described by way ofexample with reference to the accompanying drawings in which Figure 1 shows. a side view; 1

Figure 2 a front view with the air screw removed, and

Figure 3 a plan of the aeroplane, while Figures 4 and show respectively sections of a wing on the lines IV-IV and VV of Figure 3.

Referring first to Figures 1 to 3, the fuselage 1 is made as a single tube of thin sheet aluminium and carries internally an elastic motor 2 which at'the front end is connected by a hook 3 to a gear wheel 4 which gears with a smaller wheel 5. Both the wheels l and 5 are contained in a small metal casing or .gear box 6 which fits into and is loosely mounted in an opening in the front of the fuselage 1. The smaller gear wheel 5 carries on its spindle an air screw 7. It will be seen that the reaction torque exerted on the aeroplane by the air screw 7 is in the opposite sense to the torque exerted on the aeroplane by the elastic motor 2. The elastic motor aids in holding the gear box in the fuselage.

An undercarriage 8 made from a single sheet metal stamping and carrying two small metal wheels 9 is provided. The upper ends of the undercarriage fit into-small holes 10 in the fuselage.

The tail unit, including the tail plane 11 and the tail fin 12, may be caused to adhere to the fuselage in any suitable manner. The wings 13 are made hollow by bending paper double and opening it out at one end by means of a rib 14, the paper being subsequently painted or doped to impart to it the necessary rigidity. The wings are secured to the fuselage by'cross spars 15 which pass completely tl rough the fuselage, being guided in holes at either side, and enter holes in the ribs 14.

The method of imparting the desired shape or section to the wings 13 constitutes an important feature of the invention and contributes materially to the result, which is the ability of the model aeroplane to fly. This method is based upon an appreciation of the fact that the wing itself should approach as closely as possible the section and dimensions of a wing such as is used in an actual aeroplane, together with a realization of the fact that for lightness the model wing must be hollow and without any internal framework. Inthe designing of the wing the section shown in Figure 1 is taken as the basic or desirable section for the whole wing and as being that required at 4.0% of the span measured from the root of the wing, since it is at this point that the lift-drag ratio is at a maximum and that the lateral line of the centre of pressure of the 'whole wing is located It will be clearv that this desirable section cannot be obtained throughout the whole wing if at the tip the two paper surfaces are to be tightly glued together and there is no spacing rib, but it is found that by making the rib at the fuselage end of the wing of the shape shown in Figure 5 the closest approximation to the dimensions of'a real wing is obtained peak of the hyperbola constituting the top of the wing must be brought forward relatively to the peak in the basic section, and the angles at the nose of the wing must be increased relatively to the horizontal as shown.

Although we have described and shown the preferred embodiment of our invention, this has been done only for illustrative purposes and not in a limiting sense, since variations may be made within the scope of the appended claims.

-We claim:

1. In a model aeroplane, a fuselage formed at each side with at least two holes, the holes on the one side being located similarly to those on the other, two wings each provided at the inner end with a rib having holes adapted to register with the said holes in the fuselage, and rigid cross-spars extending completely through the fuselage, passing through the holes therein and entering the wings through the holes in the said ribs so as to secure the wings to the'fuselage.

2. In a model aeroplane, a fuselage consisting of a single tube devoid of any internal longitudinal framework but formed at each side withv at least twoholes, the holes on the one side being located similarly to those on the other, two wings each provided at the inner end with a rib having holes adapied to register with the said holes in the fuselage, and rigid cross-spars extending com pletely through the fuselage, passing through the:

holes therein and entering the wings through the holes in the said ribs so as to secure the wings to the fuselage.

3. In a model a'eroplaneftwo wings each consisting of a sheet of semi-rigid material folded double and having its longitudinal and outer end meeting edges stuck together and having its meetl of semi-rigid material folded double and having its longitudinal and outer end meeting edges stuck together and having its meeting edgesat the inner end held apart by a rigid rib, said ribs serving to impart the desired shape to said wings,

and means for connecting said wings to said fuselage through the medium of said ribs. 7

5. In a model aeroplane, two wings each consisting of a sheet of paper folded double and having its longitudinal and outer end meeting edges too stuck together and having its meeting edges'at' the inner end held apart by a rigid rib, said ribsserving to impart the desired shape to said wings, a fuselage, and means for connecting said wings to said fuselage through the medium of said ribs.

6. The method of making a model aeroplane wing intended to conform in use to a predetermined wing section which consists in folding double a sheet of semi-rigid material, spacing apart the meeting edges at one end by means of a spacing rib of section resembling that desired I but having its characteristics exaggerated, and sticking together the meeting edges along the length of and at the other end of the sheet, so as to form a hollow wing having itsshape imparted to it solely by the said rib.

i '7. In a model aeroplane, the combination of a fuselage, rigid cross-spars passing through .said fuselage and hollow internally structureless wings held in position by said cross-spars.

8. In a model aeroplane, the combination of I a tubular fuselage, hollow wings each provided with a root rib having apertures, and cross-spars passing through said fuselage and entering said apertures in said ribs for securing said wings to said fuselage.

9. In a model aeroplane, the combination of a tubular fuselage, hollow wings, a root rib at the inner end of each hollow wing, and instru- 'mentalitiesfor engaging the fuselage and root ribs alone for removably securing the root ribs to the fuselage.

10. In a model aeroplane, the combination of a fuselage, hollow wings, root ribs at the inner ends of the hollow wings, and instrumentalities engaging the fuselage and root ribs only of the wings, respectively, and operative to detachably I inner end of the folded sheet holding the edges of the innerend of the wing apart, said rib serving to impart the desired shape to said wings, and means for connecting said wings to said fuselage through the medium of said ribs.

12. In a model aeroplane, the combination of a fuselage, hollow wings, root ribs' at the inner ends of the hollow wings, and pins attaching the fuselage and said root ribs together through their engagement with the root ribs.

13. In a toy aeroplane, in combination, a tubular fuselage, at least two rigid members sup ported only by the walls of said fuselage and extending transversely across said fuselage, each'of "said rigid members, constituting one-half of a maleand' female socket connection, wings, root ribs at the inner ends of said wings having the other halves of said socket connections and adapted to be attached to or detached from said fuselage by relative movement between said wings and said fuselage transverse to said fuselage.

. 14. In a toy aeroplane,the combination claimed in claim 13 in which the male'members of the socket connections penetrate into the female members thereof to so small an extent as to per-' mit easy detachment of the wings-in the event of the aeroplane crashing.

15. In a toy aeroplane, a fuselage, two wings, a

root rib for each wing, and dowel connections between said fuselage and said root ribs adapted to hold said wings to said fuselage in flight but to allow said wings to be readily detached in the I event of the aeroplane crashing.

'16. In a toy aeroplane, a hollow fuselage, two

wings each-formed with a root rib, and at least two sets of. telescopic connections between said root ribs and said fuselage and operative to hold said wings to said fuselage, said connections each including a rigid member carried by and passing straight across the fuselage.

, 1'7. In a model aeroplane, two wings each consisting of a sheet of semi-rigid material folded double and having its longitudinal and outer end on each side near its bottom, an under carriage comprising a sheet metal stamping shaped to forma cradle partially embracing the lower surface of the fuselage and having diverging wheel mountings, the said stamping having projections lying in the said apertures whereby the said stamping is attached to the fuselage.

CHARLES MANDEVILLE WILMOT. JOHN MANDEVILLE WILMOT. 

